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EP0166288A2 - Bistabile Flüssigkristallspeichervorrichtung - Google Patents

Bistabile Flüssigkristallspeichervorrichtung Download PDF

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Publication number
EP0166288A2
EP0166288A2 EP85107127A EP85107127A EP0166288A2 EP 0166288 A2 EP0166288 A2 EP 0166288A2 EP 85107127 A EP85107127 A EP 85107127A EP 85107127 A EP85107127 A EP 85107127A EP 0166288 A2 EP0166288 A2 EP 0166288A2
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EP
European Patent Office
Prior art keywords
electrode
state
electrodes
liquid crystalline
liquid crystal
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Granted
Application number
EP85107127A
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English (en)
French (fr)
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EP0166288B1 (de
EP0166288A3 (en
Inventor
Kei-Hsiung Yang
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International Business Machines Corp
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International Business Machines Corp
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Publication of EP0166288A3 publication Critical patent/EP0166288A3/en
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Publication of EP0166288B1 publication Critical patent/EP0166288B1/de
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/0055—Erasing
    • G11B7/00555—Erasing involving liquid crystal media
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1343—Electrodes
    • G02F1/134309—Electrodes characterised by their geometrical arrangement
    • G02F1/134363—Electrodes characterised by their geometrical arrangement for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/13781—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering using smectic liquid crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/139—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent
    • G02F1/1391—Bistable or multi-stable liquid crystal cells
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/13725—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on guest-host interaction
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/13756—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering the liquid crystal selectively assuming a light-scattering state

Definitions

  • This invention relates to liquid crystal devices and more particularly, to a memory or storage cell embodying a liquid crystal medium.
  • phase classifications a number of different molecular alignments can occur, depending on temperature, electric field and other parameters.
  • homogeneous refers to an alignment that is parallel to the plates which are utilized in formation of the cell; whereas a homeotropic alignment occurs when the molecules are perpendicular to both of the plates.
  • focal conic texture is characterized by a disordered or scattered orientation.
  • liquid crystal display cells that can provide a variety of color states and which can operate in a storage mode, can be formed of material that has positive or negative dielectric anisotropy.
  • a smectic liquid crystal medium is discussed in that patent, such medium being disposed between electroded plates that are treated to produce parallel, that is, homogeneous alignment with. a very large tilt angle. Variation of this tilt angle, as described in that patent, can be progressively increased by increasing the strength of an applied alternating potential, thereby producing Newtonian colors when viewed through. crossed polarizers.
  • a storage mode is achieved by variation of the aforenoted tilt angle. That is to say, when the tilt is increased from an initial value, it turns out that this increase is sustained after removal of the exciting field which caused it.
  • the cell. is switched back to the original lower limit of tilt angle by a heating and cooling cycle, whereby the material goes through its nematic phase and back to the smectic phase.
  • FIG. 4 of this patent Summarizing the operation of a typical cell as disclosed in 4,291,948, the cell is capable of being switched in only one direction by the application of an alternating electric potential, while thermal cycling is used for switching in the opposite direction.
  • any storage that is achieved is based on variation of the tilt angle responsive to application of an exciting field.
  • the only exception to this is the suggestion contained in column 4 of patent 4,291,948 to the effect that certain smectic phase materials have the property of exhibiting a cross-over frequency effect in which the material exhibits positive dielectric anisotropy at low frequencies below the crossover frequency and a negative dielectric anisotropy at high frequencies above the cross- over frequency.
  • the patentee further states that with such materials, electric switching in both directions is possible.
  • any explicit teaching of bistability depends upon a heat treatment to change the stable state of the liquid crystal cell.
  • the material passes out of the energetically stable (focal conical) structure into a homeotropic-nematic orientation; and this orientation is maintained until the electric field is reduced below a second threshold value, with a brief formation of a planar-conical intermediate state.
  • a primary object of the present invention to provide a storage or memory device that is based upon the use of a liquid crystal material, preferably of the smectic phase, but depends on selective application of voltage pulses to discrete electrodes to effectuate stable states.
  • the above objects are fulfilled and implemented by a fundamental feature of the present invention according to which two stable states are provided for the cell by reason of incorporation of three electrodes within the cell structure, with connection of these three electrodes to distinct potentials.
  • the cell will develop two distinct electric field configurations responsive to the separate pulses.
  • the first stable state of the cell which is generated responsive to the application of a pulse to the second electrode, is defined as the ordered or homeotropic state of the liquid crystal;
  • the second stable state which is generated responsive to the voltage pulse applied to the third electrode, is defined as the scattered or focal conic state of the liquid crystal material.
  • the first state in the storage device as fabricated manifests itself as a dark condition, the second state as a clear or transparent condition. More specifically, the field configuration involved with the first state of the cell, is a non-uniform or "fringe" electric field; while application of a voltage pulse to the third electrode results in a uniform field because of the configuration of the third electrode.
  • the precise relationship among electrodes will be disclosed in detail hereinafter. It is sufficient to point out here that the second electrode is arranged in a mesh-like configuration. This configuration is similar to so-called inter-digitated electrode structures such as, for example, have been disclosed in the article by R. A. Soref cited herein above.
  • FIG. 3 there is illustrated the structure of a unitary cell that could constitute one of many cells in a storage array.
  • This cell structure is a three-terminal device 10 in which three distinct electrodes are provided.
  • the first of these electrodes is the top electrode 12 constituting a ground plane with respect to the entire cell structure.
  • Such ground plane is, of course, connected to ground potential.
  • a second electrode is in the form of a so-called mesh row electrode 14.
  • mesh is simply meant that the row electrode 14 as seen is formed in two thin spaced strips 14A of material, such as indium-tin oxide, the two strips being connected together to a common potential.
  • a dielectric layer 16 is interposed between the second electrode, that is, the mesh row electrode 14 and a third electrode, designated a column electrode 18, which is likewise formed of indium-tin oxide or the like.
  • This dielectric layer 16 is selected to have a thickness of approximately 1.6 micrometers (although thickness of several micrometers are possible) and with a dielectric constant of approximately 4.5.
  • a dielectric material such as Sio 2 is useful.
  • the row electrode 14 and dielectric layer 16, as well as column electrode 18, are formed in successive layers on a glass plate 20 in accordance with well known fabrication techniques.
  • the top electrode 12 is fabricated on a corresponding glass plate 22.
  • a liquid crystal material that has been selected in accordance with studies that have been conducted and samples that have been fabricated is a material known as S 2 , consisting essentially of 50% by weight of 4-cyano-4'-n-octylbiphenyl, 39% by weight of 4-cyano-4'-n-decylbiphenyl and 11% by weight of 4-cyano-4'-n-undecylbiphenyl.
  • S 2 a material known as S 2 , consisting essentially of 50% by weight of 4-cyano-4'-n-octylbiphenyl, 39% by weight of 4-cyano-4'-n-decylbiphenyl and 11% by weight of 4-cyano-4'-n-undecylbiphenyl.
  • This particular material is a smectic A phase material from -10° to 48°C. Either pure S 2' or S 2 with 1% of heptyloxy benzoic acid as an impurity, can be used
  • the fundamental capability of the device 10 as seen in FIG. 3, for operating in different stable states resides in the fact that by supplying appropriate potentials to the three electrodes therein shown, the state of the device can be changed back and forth between the ordered or homeotropic state of the liquid crystal smectic phase material and the scattered or focal conic state of such material. Thus, it is important to note that no heating of the liquid crystal material to change its phase is required. Instead, only appropriate application of different potentials to the three electrodes is necessary and sufficient. The reason for this capability is because of the different electric fields that are applied to the liquid crystal material; specifically, a fringe field, or non-uniform field, is selectively applied by appropriate selection of voltage pulses supplied to the separate electrodes; also, a uniform field is applied at appropriate times.
  • FIG. 1(b) shows the background fan texture corresponding to no-field region
  • FIG.l(b) shows the field-aligned homeotropic state. Both of these regions are transparent to the naked eye.
  • the transition region between the fan texture and the homeotropic state shows strong light scattering, which is an indication of the focal conic texture.
  • the focal conic texture was excited near the edge of the row electrode where the gradient of electric field exists (see FIG. 6).
  • FC texture unlike the nematic phase liquid crystal material, the smectic phase liquid crystal material situated at the fringe field region (again see FIG. 6) cannot bend itself to match the variation in the electric field as a function of space. Accordingly, the minimization of free energy associated with this sum of elastic energy and field energy favors the occurrence of the FC texture.
  • That picture was taken under the condition that the top electrode of the three terminal device, such as the one appearing in FIG. 3, was grounded, and a voltage pulse with amplitude of 70 volts and pulse width of 85 milliseconds was applied to the co-planar interposed fingers 14A of the row electrode 14 seen in FIG. 3.
  • the experimental results of the threshold amplitude versus pulse width to align the liquid crystal medium (S 2 + 1% heptyloxy benzoic acid) in a two-terminal device from the fan texture to the homeotropic state is shown in FIG. 2 as the lower dashed curve 30.
  • the complete alignment is shown as upper dashed curve 32.
  • the threshold amplitude versus pulse width for the generation of the FC texture by the fringe field (or field gradient) is shown in FIG. 2 as the solid curves 34.
  • the area enclosed by the solid curves represents the uncertainty of the measurement. It is clear from FIG. 2 that voltage pulses as short as one millisecond can be used to excite the FC texture by the field gradient.
  • the writing speed for a display panel-implemented by using an array of devices such as device 10 in FIG. 3 - can be fast; however, the power dissipation is quite low because the scattering FC texture is mainly generated by the gradient of the electric field.
  • This device 10 utilizes the FC texture generated by the field gradient for a display application.
  • the liquid crystal medium 24 is between a continuous conductive electrode (top electrode 12 used as a ground plane) and meshed row electrode 14, fabricated in the form of interposed strips 14A connected to a common potential.
  • the spaced parallel strips of the common electrodes 18, for example, in a typical array, are separated vertically from the meshed row electrode 14 by a dielectric layer 16, which can, for example, be Si0 2 .
  • the thickness of the liquid crystal medium 24 can be approximately 10 micrometers, the dielectric layer 16 approximately 1.6 micrometers, and the spacing between the finers 14A of row electrode 14, approximately 12 micrometers. (other thicknesses of medium 24 are possible down to two micrometers).
  • the width of the fingers 14A can be 2 micrometers (other widths are possible such as 3 micrometers).
  • a voltage pulse will strobe the meshed row electrodes 14 in a line-at-a-time fashion. It will be understood that an electrode 14 would be included in each cell in a given row; and that additional row electrodes 14 would be formed for all the other cells in the array.
  • a scattering FC texture in each of the individual cells of that row, due to the fringe field which occurs adjacent the meshed row electrodes (FIG. 61. This scattering FC texture will constitute the dark state all along the entire row. This first state will remain, even though the voltage pulse is no longer being applied to the row electrodes. However, these row electrodes will continue to be held at ground potential (FIG. 5).
  • a voltage pulse of 210 volts synchronized with and having the same pulse width as the strobing pulse applied to the particular row, is applied to the corresponding column electrode (FIG. 4).
  • the amplitude of the column voltage pulse will be approximately equal to where V 0 is the amplitude of the strobing pulse, e l and e 2 are the dielectric permitivities of the liquid crystal medium 24 and the dielectric layer 16 and h is the thickness of the dielectric layer 16, respectively.
  • this clear state will turn into a slightly scattering state when the column voltage pulse is repeatedly applied to that column electrode.
  • the electric field generated by the column voltage pulse on the clear state is screened by the mesh row electrodes.
  • the degree of screening can be determined from the detailed dimensions of d, h, g and w as seen in FIG. 3.
  • the contrast ratio of the display device or of an array embodying such individual devices can be optimized by adjusting the foregoing parameters.
  • the meshed row electrodes 14 can be replaced by any foraminated electrodes.
  • each of the conducting electrodes that is, the ground plane or first electrode 12, the meshed row or second electrode 14, and the column or third electrode 18
  • '220nm 2200 Angstroms
  • FIG. 4 shows the equal potential contours when the potentials of the meshed row electrode 14 and the column electrode 18 are at 160 volts and 210 volts respectively.
  • FIG. 5 shows the case where the column electrode 18 is at 210 volts and the meshed row electrode 14 is grounded. Using this FIG. 5, a rough estimate of the electric field line reveals that the focal conic texture will be generated near the edge of the meshed row electrode, as depicted by the dashed curve double loops A seen in that figure.
  • FIG. 6 illustrates the case where the meshed row electrode is at 160 volts and the column electrode is floating.
  • the region where the focal conic texture is likely to form by reason of the field gradients is indicated as the region B between the dashed line shown in FIG. 6 and the dielectric layer 16.
  • FIGS. 4 and 6 represent the clear and dark states respectively of the liquid crystal layer 24; the estimated achievable contrast ratio of the device is approximately 3 to 1.
  • An alternate implementation of the device so as to improve the contrast ratio can be accomplished by changing the top ground plane of FIG. 3, into a sectionalized row electrode having multiple strips-in parallel alignment with the respective strips of the meshed row electrode.
  • the strobed meshed row electrode 14 is at a high voltage, while the corresponding strobed, aligned top row electrode 12 is grounded.
  • the equi-potential contours are similar to those shown in FIG. 6.
  • both the meshed row electrode 14 and the top row electrode 12 are floating so that column voltage pulses applied on the column electrodes 18 can hardly affect the liquid crystal medium situated at the position of the non-strobed rows.
  • the clear state is shown in FIG. 4.
  • FIG. 7 a simplified array of cells embodying the devices 10, previously seen in FIG. 3, is illustrated.
  • This is an exemplary 2X2 array in which four cells are connected in a conventional coordinate arrangement.
  • a bit line driver is connected to the lines 100 and 102 and thence to the column electrodes 18 of the individual cells in the respective columns.
  • a word line driver is selectively connected to the lines 104 and 106 which, in turn, connect to the row electrodes 14 of the cells in the respective rows.
  • the pulse output from the word line driver having a value of 160 volts, is applied selectively to the word lines 104 and 106 at the respective times Tl and T2. At other times, zero volts is applied to each of the lines 104 and 106. Accordingly, when 210 volts is simultaneously applied at the time Tl to the bit line 100, then cell 1 will be placed in the second or clear state for the reasons already explained. On the other hand, if at the same time Tl, a floating potential is applied to the bit line 102 and thereby to the column electrode 18 of cell 2 then, for reasons already explained, cell 2 is in the first or dark state.
  • the cell structure of FIG. 3 can be made.
  • four electrodes can be provided; specifically, by adding an extra row electrode adjacent to the top of the liquid crystal layer 24 and by spacing the ground plane 12 from that additional row electrode by a further layer of dielectric material.
  • the liquid crystal medium involved in the device cells can include dichroic dyes for color display purposes.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Theoretical Computer Science (AREA)
  • Geometry (AREA)
  • Mathematical Physics (AREA)
  • Liquid Crystal (AREA)
EP85107127A 1984-06-29 1985-06-11 Bistabile Flüssigkristallspeichervorrichtung Expired - Lifetime EP0166288B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US06/626,161 US4617646A (en) 1984-06-29 1984-06-29 Electric field gradient excited liquid crystal cell having bistability
US626161 1984-06-29

Publications (3)

Publication Number Publication Date
EP0166288A2 true EP0166288A2 (de) 1986-01-02
EP0166288A3 EP0166288A3 (en) 1988-05-04
EP0166288B1 EP0166288B1 (de) 1992-08-26

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EP0257638A2 (de) * 1986-08-27 1988-03-02 Canon Kabushiki Kaisha Vorrichtung zur optischen Modulation
EP0425321A2 (de) * 1989-10-27 1991-05-02 The Mead Corporation Flüssigkristallzellen und ihre Anwendung zur Aufzeichnung von Information oder Lichtbildprojektion

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JPS62112128A (ja) * 1985-11-11 1987-05-23 Semiconductor Energy Lab Co Ltd 液晶装置
US4878742A (en) * 1986-08-04 1989-11-07 Canon Kabushiki Kaisha Liquid crystal optical modulator
DE3750006T2 (de) * 1986-08-25 1994-10-06 Canon Kk Optische Modulationsvorrichtung.
JPS63168628A (ja) * 1987-01-05 1988-07-12 Semiconductor Energy Lab Co Ltd 液晶装置
JPS63168630A (ja) * 1987-01-05 1988-07-12 Semiconductor Energy Lab Co Ltd 液晶装置およびその駆動方法
US5122888A (en) * 1987-07-10 1992-06-16 Canon Kabushiki Kaisha Focusing plate having phase grating formed by using liquid crystal
JP2605723B2 (ja) * 1987-07-22 1997-04-30 日本電気株式会社 薄膜トランジスタアレー形液晶表示装置
US5084778A (en) * 1989-12-26 1992-01-28 General Electric Company Electrode structure for removing field-induced disclination lines in a phase control type of liquid crystal device
US5274484A (en) * 1991-04-12 1993-12-28 Fujitsu Limited Gradation methods for driving phase transition liquid crystal using a holding signal
US6704083B1 (en) * 1997-05-30 2004-03-09 Samsung Electronics, Co., Ltd. Liquid crystal display including polarizing plate having polarizing directions neither parallel nor perpendicular to average alignment direction of molecules
TW434443B (en) * 1997-05-30 2001-05-16 Samsung Electronics Co Ltd Liquid crystal display
DE19861477B4 (de) * 1997-05-30 2014-02-13 Samsung Display Co., Ltd. Flüssigkristallanzeige
KR100254856B1 (ko) 1997-05-30 2000-05-01 김영환 액정 표시 소자
CN1173216C (zh) 1997-11-03 2004-10-27 三星电子株式会社 具有改变的电极排列的液晶显示器
US6147666A (en) * 1997-12-22 2000-11-14 Yaniv; Zvi Multipole liquid crystal display
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0234429A2 (de) * 1986-02-17 1987-09-02 Sel Semiconductor Energy Laboratory Co., Ltd. Flüssigkristallvorrichtung mit einer Ladungs-Speicherstruktur
EP0234429A3 (en) * 1986-02-17 1989-11-15 Sel Semiconductor Energy Laboratory Co., Ltd. Liquid crystal device with a charge strage structure
EP0257638A2 (de) * 1986-08-27 1988-03-02 Canon Kabushiki Kaisha Vorrichtung zur optischen Modulation
EP0257638A3 (en) * 1986-08-27 1988-12-14 Canon Kabushiki Kaisha Optical modulation device
EP0425321A2 (de) * 1989-10-27 1991-05-02 The Mead Corporation Flüssigkristallzellen und ihre Anwendung zur Aufzeichnung von Information oder Lichtbildprojektion
EP0425321A3 (en) * 1989-10-27 1993-02-24 The Mead Corporation Liquid crystal cells and their use for recording information or for projecting an image

Also Published As

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DE3586552T2 (de) 1993-04-08
JPH0623818B2 (ja) 1994-03-30
JPS6115127A (ja) 1986-01-23
DE3586552D1 (de) 1992-10-01
EP0166288B1 (de) 1992-08-26
CA1241727A (en) 1988-09-06
US4617646A (en) 1986-10-14
EP0166288A3 (en) 1988-05-04

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